1. Field of the Invention
The present invention concerns cameras equipped with sensors, for example of the CCD sensor type (charge coupling sensors), CMOS sensor type (Complementary Metal Oxide Semiconductor) or cameras of the video camera type. These sensors are grouped together in the remainder of the present text under the generic term photosensitive sensors. They supply signals representing an image that can then be processed. They are generally sensitive in the visible range and/or in the infrared range, in particular in the near infrared.
2. Description of the Related Art
This type of photosensitive sensor is being included more and more frequently in motor vehicles. The images obtained can be processed to allow the display of images on screens, for example at the dashboard or projected on the windscreen, in particular to alert the driver in the case of danger or simply to improve his visibility. The images can also make it possible to detect raindrops on the windscreen.
These images can participate in the automatic triggering of a functionality of the vehicle (alert to the driver, automatic triggering of braking, automatic triggering of the windscreen wipers in the case of the display of drops of water on the windscreen, visual or audible warning, control of certain functions of the headlight, etc).
These sensors can be used by day. They can also be used at night, and it is then possible to use their capacities to detect radiation in the infrared. In nocturnal use, these sensors thus participate for example in the “night vision” functionality (or “night vision” in English), where the images, once processed, are projected onto a display screen generally in the form of black and white images.
It can be seen by these very varied applications that it is desirable, but very difficult in practice, to use a single sensor to implement several of these applications, since the image capture parameters vary considerably according to the application.
Let us take an application concerning in particular the present invention, namely the use of a sensor for detecting any drops of water on the vehicle windscreen, in order to automatically control the functioning of the wipers: The sensor is generally installed in the vehicle close to the windscreen, for example around twenty centimeters from it, and it is therefore associated with a lens focused on the windscreen in order to be able to detect precisely the drops of water on the windscreen, their contours, their size, etc. On the other hand, if it is wished to use a sensor for taking images of the road, that is to say far-field images through the windscreen, it is necessary on this occasion to associate with the sensor a lens focused on infinity.
Use is therefore made of dedicated sensors, one per application, which increases the cost, the size and the complexity of the equipment of the vehicle, the size being not the least of the drawbacks since the space available close to the windscreen is often very limited.